Container formed of paper based material having coating to protect led chips from sulfurous emission

ABSTRACT

A method and system for storing an electronic device, such as an LED  34  component having metallic conductive leads  36, 38  or a light engine  30  having LEDs soldered to a PCB  32,  within a container  100  formed of paper material. The container interior surface  14, 16  is coated with a barrier  20  bounding the interior volume  18.  Barrier  20  occludes an emission of sulfur-containing gas from the paper material into interior volume  18.  Barrier  20  is a polymer, e.g. a thermoplastic material, either in the form of a sheet or a spray or liquid coating, preferably applied to the paper material blank  10  before it is folded into the container shape  100.  Barrier  20  may further comprise electro-static discharge material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United States provisional application Ser. 62/876,100, filed Jul. 19, 2019, whose contents are hereby incorporated by reference.

TECHNICAL FIELD

A container formed of paper material, such as paperboard or cardboard, coated on its inside surfaces to provide a protective barrier for electronic devices stored within the container from sulfur-containing emissions.

BACKGROUND

It is known in Osram Opto Semiconductors Application Note No. AN005 entitled “Preventing LED Failures Caused by Corrosive Materials”, published Jan. 18, 2018, that corrosive gases such as hydrogen sulfide (H2S) in packaging materials can damage electronic devices. For example, hydrogen sulfide can penetrate through the encapsulation of a solid-state lighting device such as a light emitting diode (LED), especially when a silicone encapsulation is used. This can lead to corrosion of the different metals used in the LED. If gases diffuse through the encapsulation, the lead frame may become discolored. For example, silver-plating on the leads can react with sulfur compounds, causing a chemical reaction that transforms the silver into silver sulfide, darkening the lead. In the case of individual, unprocessed electrical components this can lead to difficulties later in soldering leads to circuit boards. In the case of processed electrical components, such as LEDs that have been soldered to a PCB, this can lead to electrical failure. Because silver sulfide is not electro-conductive, and its volume is greater than the volume of silver, this can lead to a mechanical separation between the bond wire and the connecting lead on the printed circuit board (PCB), resulting in an open circuit. Many LEDs contain a phosphor coating which determines its color temperature. Discoloration of the silver-plated leads can cause the phosphor to discolor which can alter or shift the desired correlated color temperature (CCT) of the LED chip, lead to a loss of brightness, and deteriorate the chip.

Common paper or paperboard packaging can be a source of corrosion due to outgas sing of sulfur or sulfur-containing gaseous substances. Paper made by the Kraft process, which is also known as Kraft pulping or sulfate process, is made by converting wood or vegetable pulp (e.g. comminuted wood, straw, bamboo, or other organic fibrous material) by treatment with a hot mixture of water, sodium hydroxide, and sodium sulfide to break the lignin bonds, as generally disclosed in e.g. U.S. Pat. No. 296,935 (Dahl). Pulp produced by the Kraft process is known to be strong, with its strength dependent on maintaining a high effective sulfur ratio or sulfidity during processing. Without the desire to be bound to any particular theory, it is believed that residual sulfur-containing material (whether sulfur or compounds containing sulfur such as hydrogen sulfide) can, as a result of the pulping process, later outgas from inside the container formed from the paper.

Known techniques to avoid sulfur-containing gas from coming into contact with an electronic device, especially contact with the metallic conductive elements of an electronic device or parts of LEDs, have been recommendations to not store electronic components in cardboard boxes for more than a very limited amount of time even to the point of recommending to discard LEDs that have remained in corrugated cardboard for more than 10 days. This is impractical and inconvenient since shipping and storing from component supplier to the factory may typically be more than 10 days. Alternative recommendations to partially mitigate these problems have included selecting more expensive corrugated cardboard that contains less than 850 ppm (parts per million) sulfur. Oher techniques to avoid sulfur-containing gas contact is the use of a plastic bag (referred to in the art as a liner) placed loosely as a separate component inside the container formed of paper. This remedy is expensive and labor-intensive since it involves the cost, use, handling and placement of an additional piece-part, and requires choosing a plastic bag of different sizes depending on the size of the objects placed in the container, ranging e.g. from small piece-parts such as resistors or memory chips or LED components to larger sub-assemblies such as light engines in which a plurality of LEDs are mounted on a printed circuit board. Other inconvenient approaches involve avoiding entirely the use of a container formed from paper material in favor of using a container made out of plastic, but which may be much more expensive than a paper container, environmentally less friendly, and requires careful selection to avoid chemicals therein that may react with metallic leads or LEDs.

ACKNOWLEDGED PRIOR ART

It is known in the storing and shipment of foods and chemicals in containers formed of paper to provide a Modified Atmosphere Packaging (MAP). An example of MAP is known in U.S. Pat. No. 5,609,293 (Wu) disclosing a polymer liner directly bonded to a paperboard container, such as a polyethylene film laminated to the inside surfaces of a Kraft paper box; as disclosed in FIG. 1 therein, the innermost layer is exposed paper (5), the polyethylene layer (6) is sandwiched to an underlayer of corrugated paper plies (4, 8, 10) forming a MAP container for broccoli. As is known in the art, the polymer film can be applied from rollers in sheet form to cardboard blanks or as a melted liquid plastic.

Other MAP containers are known for use with chemicals e.g. for hygroscopic protection of dry laundry detergent, as in United Kingdom Patent GB 1 590 880 (Chakraborti), disclosing a cardboard, paperboard or similar board material container whose inner first layer or outer third layer is a composite laminate consisting of two sheets of the board material between which is sandwiched a polyethylene moisture barrier. Other MAP containers for foodstuffs, such as liquids, or chemicals have a layer of thermoplastic co-extruded film (1-3 mil thickness) as a moisture barrier applied to the paper board material, as in U.S. Pat. 4,871,406 (Griffith), disclosing the film can be high density polyethylene, polypropylene, or polyethylene terephthalate.

Another form of MAP container is known for the cold storage and transport of fruits such as table grapes in which an elevated sulfurous environment is intended to be maintained within the cardboard box, as disclosed in the article “Evaluation of Table Grape Storage in Boxes with Sulfur Dioxide-releasing Pads with Either an Internal Plastic Liner or External Wrap”, Lichter et al., published in HortTechnology (April-June 2008) Vol. 18(2) at pp. 206-214. The sulfur dioxide-releasing pad generates an elevated SO2 level within the container to provide a fumigation effect preventing mold during storage. This article discloses, see abstract, table 5 and FIG. 3 therein, that excess moisture condensation or growth of mold can be prevented by either (a) a cardboard box within which a loose, perforated polyethylene bag, which is perforated to allow limited vapor transmission, contains the grapes and the sulfur dioxide-releasing pad, or (b) packing the grapes and sulfur dioxide pad inside the cardboard box which is then externally pallet-wrapped with low density polyethylene film on the sides and top but leaving the box bottom unwrapped to allow vapor transmission, avoiding condensation.

SUMMARY

Embodiments herein provide a method and system for storing an electronic device, such as an LED component having metallic conductive leads or a light engine having LEDs soldered to a PCB, within a container formed of paper material. The container interior surface is coated with a polymer such as a thermoplastic material, either in the form of a sheet or a spray or liquid coating, preferably applied to the paper material blank before it is folded into the container shape. The barrier may further comprise electro-static discharge material.

BRIEF DESCRIPTION OF FIGURES

The above-mentioned and other features of this disclosure, and the manner of attaining them, will become apparent and better understood by reference to the following description of embodiments described herein in conjunction with the drawings, wherein:

FIG. 1 shows an unfolded paper carton blank 10 having barrier 20;

FIG. 2 shows folded paper container 100 formed from blank 10;

FIG. 3 shows light engine 30 and its LEDs 34 with metallic leads 36, 38;

FIG. 4 show an electronic device 50 having metallic conductive leads 52; and

FIG. 5 shows container 100 with plural light engines 30 in its interior volume 18.

DETAILED DESCRIPTION INCLUDING BEST MODE OF A PREFERRED EMBODIMENT

The present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The embodiments herein may be capable of being practiced or being carried out in various ways. Also, it may be appreciated that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting as such may be understood by one of skill in the art.

FIG. 1 shows carton paper blank 10 in unfolded state, and FIG. 2 shows assembled container 100 having an interior volume 18 to receive stored electronic articles. Blank 10 is conveniently scored as is known in the art. Blank 10 has main panels 12 that when folded define principal lateral sides of container 100, and top flaps 14 that define an upper panel of container 100 and bottom flaps 16 that define an upper surface of container 100, all as known in the art. Container blank 10 optionally has additional latching flaps for gluing or sealing container 100 securely. The panels that define and bound interior volume 18 are provided with barrier 20. Barrier 20 is the innermost layer of container 100. Barrier 20 preferably comprises a polymer, more preferably a thermoplastics material.

Container 100 is formed of paper material, as described hereinabove. Blank 10 is suitably formed of paper, Kraft paper, paperboard, cardboard, corrugated cardboard, or molded fibers (akin to conventional egg cartons), or the like. It is not relevant if the paper material originated from a tree or other organic raw feed source. Paperboard is typically lighter because it uses only a single layer of boxboard pressed together, which is used for packaging smaller, light items, somewhat akin the weight of material for a cereal box or such everyday products as tissue boxes. Cardboard, with its more heavy-duty material, is made of several layers of paper on one side, sandwiching corrugated or waffle-like texture in the middle and another layer or multiple layers of paper on the other side. Since it is thicker and less likely to tear or break, it is used for packaging bigger, bulkier or heavier items. The term paper material, as used herein, is not intended to be limiting as to a particular form of paper sheet or panel material.

Barrier 20 in assembled container 100 occludes transmission of sulfur-containing gas emitted from the paper material into interior volume 18 where an electronic device 34 or 50 is stored. The term sulfur-containing gas includes sulfur or a compound of sulfur, e.g. hydrogen sulfide. Such sulfur-containing gas can be emitted from the paper material, as described hereinabove. Barrier 20 can for example comprise polyethylene, whether low density (LDPE) or high density (HDPE). Barrier 20 can also comprise polyethylene terephthalate (PET), e.g. polyester. Barrier 20 may also contain variants of these polymers that are electro-static discharge (ESD) treated, such as having conductive polystyrene (PS); an Inherently Conductive Polymer-Polystyrene (ICP-PS) additive; conductive HDPE; conductive acrylonitrile butadiene styrene/thermoplastic elastomer (ABS/TPU); or high impact polystyrene (HIPS).

Barrier 20 material is coated onto paper blank 10 in the form of a film that is rolled onto paper blank 10, or alternatively as a melted liquid plastic that solidifies, as generally known in the art, such as disclosed in U.S. Pat. No. 5,609,293 (Wu) and U.S. Pat. No. 4,871,406 (Griffith), each of which is incorporated by reference as if fully set forth herein. Such techniques are readily known to those of skill in the carton arts. As also known in the art, suitable thickness of barrier 20 is chosen to provide low vapor transmission rate to sulfur-containing gas. In assembled condition of container 100, coated barrier 20 is the innermost surface that defines or bounds interior volume 18.

FIG. 3 and FIG. 4 illustrate electronic devices having a metallic electrically conductive element such as leads, capable of storage in container 100. FIG. 3 depicts light engine 30 having a plurality of LEDs 34 mounted on printed circuit board (PCB) 32 by their leads 36, 38 soldered to traces (not shown) on PCB 32 as known in the art. A poke-in connecter 40 is also mounted with its leads connected to PCB 32, for the coupling of wires for supply of power or signals to PCB 32. Other examples of an electronic device that may be required to be stored in paper container 100 is an electrical resistor, which also has electric leads, or as shown in FIG. 4 a processor chip 50 having leads 52. The exact construction or type of the device to be stored in container 100 is generally not important, as the object achieved by the coated container 100 remains being to protect the device's electrical conductive elements from corrosive sulfur-containing gas. As is known in the art, the leads can be made of copper or other suitable conductive metallic material and can be coated such as with tin or silver to enhance solder connections. Container 100 may store loose, unassembled electronic devices or subassemblies on which electronic devices such as LEDs 34 are affixed to PCB 32.

FIG. 5 shows that container 100 may conveniently contain within its interior volume 18 multiple electronic devices such as light engines 30 on shipping trays 55.

While a preferred embodiment of the present disclosure has been described, various changes, adaptations and modifications can be made therein without departing from the spirit of the disclosure and the scope of the appended claims. The scope of the disclosure should be determined not with reference to the above description, but instead with reference to the appended claims along with their full scope of equivalents. It also should be understood that the appended claims do not necessarily set forth the broadest scope of the disclosure which the applicant is entitled to claim, or the only manner in which the disclosure may be claimed, or that all recited features are necessary.

The following is a non-limiting list of reference numeral used herein:

-   -   10 paperboard or cardboard blank     -   12 main panels of blank 10     -   14 top flaps of blank 10     -   16 bottom flaps     -   18 interior volume     -   20 barrier (film or coating)     -   30 light engine     -   32 printed circuit board (PCB)     -   34 light emitting diode (LED)     -   36 electrical lead of LED 34     -   38 electrical lead of LED 34     -   40 poke-in connector     -   50 electronic device     -   52 electrical leads of electronic device     -   55 tray for electronic device     -   100 container 

What is claimed is:
 1. A method of storing or transporting an electronic device having a metallic electrically conductive element in a container formed from a paper material, comprising forming a container of a paper material, the container having an interior volume; coating, with a barrier, an interior surface adjacent the interior volume of the container; disposing, inside the interior volume, an electronic device having a metallic electrically conductive element; and occluding, by action of the barrier, an emission of sulfur-containing gas from the paper material into the interior volume.
 2. The method of claim 1, wherein the container comprises paperboard.
 3. The method of claim 1, wherein the container comprises cardboard.
 4. The method of claim 3, wherein the cardboard comprises corrugated cardboard.
 5. The method of claim 1, wherein the coating comprises coating the interior surface with a polymer.
 6. The method of claim 5, wherein the polymer is selected from the group of materials polyethylene terephthalate (PET) and polyethylene (PE).
 7. The method of claim 5, wherein the polymer comprises electro-static discharge material.
 8. The method of claim 1, wherein the electronic device comprises at least one light emitting diode (LED).
 9. The method of claim 8, wherein the electronic device comprises a light engine.
 10. A system for storing or transporting an electronic device, the system comprising: a container formed from a paper material and defining an interior surface; a barrier coated on the interior surface, the barrier occluding a transmission of sulfur-containing gas; and an electronic device disposed within the container, the electronic device comprising at least one metallic electrically conductive element.
 11. The system of claim 10, wherein the container comprises paperboard.
 12. The system of claim 10, wherein the container comprises cardboard.
 13. The system of claim 12, wherein the cardboard comprises corrugated cardboard.
 14. The system of claim 10, wherein the barrier comprises a polymer.
 15. The system of claim 14, wherein the polymer is selected from the group of materials polyethylene terephthalate (PET) and polyethylene (PE).
 16. The system of claim 14, wherein the polymer comprises electro-static discharge material.
 17. The system of claim 16, wherein the electro-static discharge material is selected from the group of materials conductive polystyrene (PS); inherently conductive polymer-polystyrene (IPS-PS) additive; conductive high-density polyethylene (HDPE); conductive acrylonitrile butadiene styrene/thermoplastic elastomer (ABS-TPU); and high impact polystyrene (HIPS).
 18. The system of claim 10, wherein the electronic device comprises at least one light emitting diode (LED).
 19. The system of claim 18, wherein the electronic device comprises a light engine.
 20. The system of claim 10, wherein the coated barrier defines an innermost surface bounding an interior volume of the container. 